Analysis of mitochondrial genomes resolves the phylogenetic position of Chinese freshwater mussels (Bivalvia, Unionidae)

The Yangtze River basin is one of the most species-rich regions for freshwater mussels on Earth, but is gravely threatened by anthropogenic activities. However, conservation planning and management of mussel species has been hindered by a number of taxonomic uncertainties. In order to clarify the taxonomic status and phylogenetic position of these species, mitochondrial genomes of four species (Acuticosta chinensis, Schistodesmus lampreyanus, Cuneopsis heudei and Cuneopsis capitatus) were generated and analyzed along with data from 43 other mitogenomes. The complete F-type mitogenomes of A. chinensis, S. lampreyanus, C heudei, and C capitatus are 15652 bp, 15855 bp, 15892 bp, and 15844 bp, respectively, and all four F-type mitogenomes have the same pattern of gene arrangement. ML and BI trees based on the mitogenome dataset are completely congruent, and indicate that the included Unionidae belong to three subfamilies with high bootstrap and posterior probabilities, i.e., Unioninae (Aculamprotula, Cuneopsis, Nodularia, and Schistodesmus), Anodontinae (Cristaria, Arconaia, Acuticosta, Lanceolaria, Anemina, and Sinoanodonta), and Gonideinae (Ptychorhynchus, Solenaia, Lamprotula, and Sinohyriopsis). Results also indicate that A. chinensis has affinities with Arconaia lanceolata and Lanceolaria grayii and is a member of the subfamily Anodontinae.